From: Richard Henderson <rth@twiddle.net>
To: Heiher <r@hev.cc>, qemu-devel@nongnu.org
Cc: yongbok.kim@imgtec.com, Heiher <wangr@lemote.com>, aurelien@aurel32.net
Subject: Re: [Qemu-devel] [PATCH] linux-user: Fix do_store_exclusive for shared memory of interprocess.
Date: Tue, 18 Oct 2016 10:55:21 -0700 [thread overview]
Message-ID: <20f1348e-a027-f53a-d558-b471d0b19051@twiddle.net> (raw)
In-Reply-To: <20161015155348.26834-1-r@hev.cc>
On 10/15/2016 08:53 AM, Heiher wrote:
> + if ((__hptr = lock_user(VERIFY_WRITE, __gaddr, sizeof(target_type), 0))) { \
> + if ((old) != atomic_cmpxchg(__hptr, (old), (new))) \
> + __ret = -TARGET_EAGAIN; \
> + unlock_user(__hptr, __gaddr, sizeof(target_type)); \
This doesn't perform an atomic operation, because lock_user and unlock_user
copy data from and to the guest. The atomic operation you're doing is on
memory private to the host.
You also have to handle host byte order != target byte order.
That said, we are some way toward addressing this. The patch set that Emilio
pointed you at is a good start.
r~
prev parent reply other threads:[~2016-10-18 17:55 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-15 15:53 [Qemu-devel] [PATCH] linux-user: Fix do_store_exclusive for shared memory of interprocess Heiher
2016-10-15 16:04 ` no-reply
2016-10-16 20:34 ` Emilio G. Cota
2016-10-18 17:55 ` Richard Henderson [this message]
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